Various types of conveyors have been devised which employ an elongate tray or pan having a planar surface for transporting goods thereon. These trays conventionally have sides projecting upwardly from the planar floor of the tray, such that the tray has a generally U-shaped cross-sectional configuration. Conveyors with these types of trays are preferred for various applications since the goods transported along the tray need only engage the tray during the conveying operation, and since the tray may be easily cleaned.
One type of conveyor which utilizes such a tray is a vibratory conveyor or shaker conveyor. These types of conveyors utilize a drive mechanism which essentially vibrates the tray, so that goods move along a slightly inclined or horizontal tray floor due to the forward direction imparted to the goods while raised off the floor. An earlier version of a conveyor drive is disclosed in U.S. Pat. No. 2,374,663, which utilizes a pair of crank arms. The crank arm causes a change in the rotational speed of a driven pulley. Other drives for a vibratory conveyor system are disclosed in U.S. Pat. Nos. 4,260,052, 4,913,281, 5,404,996, 6,019,216, 6,230,875, 6,276,518, 6,415,912, and 6,435,337. More recent drives for vibratory conveyors are disclosed in U.S. Pat. Nos. 6,719,124 and 6,868,960. U.S. Pat. No. 4,917,655 is directed to a timing belt tensioner.
Differential impulse conveyors have significant advantage over vibratory conveyors for many applications. Differential impulse conveyors slide goods along a tray, but do not require vertical movement of the goods with respect to the tray. Goods conveyed with a differential impulse conveyor are thus generally subject to less damage than goods transported by a vibratory conveyor. Moreover, the drive mechanism itself may operate in a quieter manner and may be less susceptible to maintenance problems. An early version of a drive for an inertial conveyor is disclosed in U.S. Pat. No. 5,178,278. Drives for differential impulse conveyors are disclosed in U.S. Pat. Nos. 5,794,757, 6,079,548, 6,189,683, 6,398,013, 6,415,911 and 6,527,104. Another type of differential impulse conveyor drive is disclosed in U.S. Pat. No. 7,216,757.
The disadvantages of the prior art are overcome by the present invention, and an improved differential impulse conveyor and a drive for such a conveyor are hereinafter disclosed.